This invention relates generally to suppressing electromagnetic interference (EMI) within a computer system. In particular, the present invention is an EMI suppressing bulkhead plate member for a peripheral component interconnect (PCI) computer system housing. The bulkhead plate member provides EMI containment at a telephone jack connector affixed to a printed circuit board (PCB) mounted within the PCI computer system housing.
As computer system frequencies and power increase, the electromagnetic energy or noise, also known as electromagnetic interference (EMI), radiating from the computer system housing increases proportionally. This EMI noise typically originates from the different components within the computer system, and can interfere with the operation of other pieces of electronic equipment associated with the computer system or in close proximity thereto. As such, computer systems typically need to comply to an electromagnetic compliance (EMC) standard which defines limits to levels of stray EMI noise. To comply with EMC standards and to protect electronic equipment from operation affecting EMI noise, the computer system components that emit EMI noise are generally placed within a shielded enclosure, such as a computer system housing. The computer system housing suppresses EMI noise emanating from computer system components by containing or otherwise diminishing stray EMI noise signals.
One type of computer system housing that attenuates EMI noise employs a PCB input/output (I/O) connection system known as the peripheral component interconnect (PCI) system. The popularity of the PCI system has grown to a point where it is the preferred I/O connection system for larger server computers as well as workstation computers. The PCI system allows one or more microprocessors (i.e., PCB""s) to be interconnected with attached external devices.
The PCI system includes a computer system housing defined by a plurality of walls. At least one of these walls is removable to provide access to an interior region of the housing to allow PCB""s to be inserted into and removed from the housing. The PCB""s are releasably connectable to a central processing unit of the computer system through a mother board, often referred to as a backplane board, as it is vertically mounted as a back wall of the computer system housing.
A wall of the computer system housing adjacent to the backplane board includes a plurality of PCI slots (i.e., between six and twelve total) which are disposed in the computer system housing to provide external access to the PCB""s mounted within the housing. Peripheral component connectors on the PCB""s extend through these PCI slots so that compatible external devices can be plugged into the PCB""s via the peripheral component connectors. On type of peripheral component connector typically used in computer system housings is a telephone jack connector often referred to as a RJ-45 connector.
The wall of the computer system housing that includes the PCI slots is often referred to as the bulkhead wall of the computer system housing. In the PCI system, that portion of a PCB that includes the peripheral component connector also includes a bulkhead plate member that covers the portion of the respective PCI slot not taken up by the peripheral component connector. In addition, in the PCI system, those PCI slots not currently accommodating a PCB are covered by individual blank bulkhead plate members that are substantially identical to the PCB bulkhead plate members and function to cover the unused PCI slots. The PCB and blank bulkhead plate members are typically secured to the housing, and in particular, to the bulkhead wall via a separate screw fastener.
The walls of the PCI computer system housing generally provide some suppression of the EMI noise produced by the PCB""s mounted within the housing. However, EMI noise from the PCB""s does radiate from the PCI slots and the peripheral component connectors (e.g., RJ-45 connectors) to such an extent that a typical PCI computer system housing does not meet EMC standards. To provide conduction paths to the computer system housing for EMI noise currents to meet EMC standards, bulkhead gaskets are used.
In the typical PCI system, the bulkhead gasket is placed on the interior surface of the bulkhead wall. The bulkhead gasket makes contact with the bulkhead wall and with the bulkhead plate members along the two longest sides of the bulkhead plate members. Typically, the bulkhead gasket is a thin (0.004xe2x80x3) stainless steel metal stamping containing a line of formed spring tabs as contact points between the bulkhead wall and the bulkhead plate members. The peripheral component connectors typically extend through oversized openings within the bulkhead plate members. In the case of RJ-45 peripheral component connectors, these connectors typically include spring fingers that make contact with edges of the oversized openings in the bulkhead plate members to provide EMI noise containment.
FIG. 1 generally illustrates a partial sectional view of a prior art bulkhead plate member 100 and a RJ-45 peripheral component connector 102 mounted to a PCB 104 as referred to above. The bulkhead plate member 100 includes a main portion 106 defining an oversized opening 108 sized to allow the RJ-45 connector 102 to extend therethrough. The bulkhead plate member 100 further includes a mounting tab 110 that extends at a 90xc2x0 angle with respect to the main portion 106. The mounting tab 110 includes a slot 112 for receipt of a fastener (not shown) for mounting the bulkhead plate member 100 to a PCI computer system housing (not shown). As can be seen in FIG. 1, side walls 114 (only three of which can be seen) of the RJ-45 connector 102 include EMI spring fingers 116. Each side wall 114 includes a pair of EMI spring fingers 116 which contact edges 118 of the oversized opening 108.
Because the bulkhead plate member 100 is very thin (i.e., 0.030xe2x80x3) there is very little surface area contact between the EMI spring fingers 116 and the edges 118 of the oversized opening 108 in the bulkhead plate member 100. As a result, EMI noise containment around the RJ-45 connector is generally inadequate and may not comply with EMC standards. Without adequate contact between the bulkhead plate members and the EMI spring fingers of the RJ-45 connector, EMI noise will not be conducted to the computer system housing, and as such, the EMI noise will not be suppressed.
There is a need for an improved PCI computer system housing. In particular, there is a need for PCI bulkhead plate members that adequately suppresses EMI noise around peripheral component connectors, such as RJ-45 telephone jack connectors. The PCI bulkhead plate member should permit ample surface area contact between the bulkhead plate member and the EMI spring fingers on the RJ-45 connector to maximize the attenuation of EMI noise.
The present invention is a bulkhead plate member for providing an attenuating barrier for electromagnetic interference (EMI) noise in a computer system housing. The bulkhead plate member includes a rectangular shaped main portion having a material thickness. The main portion has a plurality of edge walls defining an opening for receiving a peripheral component connector affixed to a printed circuit board (PCB). The edge walls are adapted to contact side walls of the peripheral component connector to provide contact regions substantially perpendicular to the main portion and greater than the material thickness of the main portion, such that EMI noise is conducted through the bulkhead plate member, at the edge walls of the opening, to a bulkhead wall of the computer system housing thereby suppressing the EMI noise.
In one aspect of the present invention, the bulkhead plate member also includes a first mounting tab at a first end of the main portion, and a second mounting tab at a second opposite end of the main portion. The second mounting tab extends at substantially a 90xc2x0 angle with respect to the main portion. In another aspect of the present invention, the edge walls of the opening in the main portion of the bulkhead plate member are flange elements that are integral with the main portion. These flange elements engage spring fingers on side walls of the peripheral component connector. In a further aspect of the present invention, the peripheral component connector is a RJ-45 telephone jack connector.
In another embodiment, the present invention provides a computer system housing for providing an attenuating barrier for electromagnetic interference (EMI) noise. The computer system housing includes a backplane wall having a plurality of connectors for receiving PCB""s, and a bulkhead wall coupled to the backplane wall. The bulkhead wall defines a plurality of bulkhead slots through which connector receptacles of the PCB""s can extend. The computer system housing also includes a plurality of bulkhead plate members. At least one of the bulkhead plate members includes a rectangular shaped main portion having a material thickness. The main portion has a plurality of edge walls defining an opening for receiving a peripheral component connector affixed to a printed circuit board (PCB). The edge walls are adapted to contact side walls of the peripheral component connector to provide contact regions substantially perpendicular to the main portion and greater than the material thickness of the main portion, such that EMI noise is conducted through the bulkhead plate member, at the edge walls of the opening, to a bulkhead wall of the computer system housing thereby suppressing the EMI noise.
In this bulkhead plate member and computer system housing of the present invention, the edge walls (i.e., flange elements) defining the opening in the main portion of the bulkhead plate member provide an increased amount of surface area contact between the bulkhead plate member and the spring fingers on the side walls of the RJ-45 telephone jack connector. This increased surface area contact substantially maximizes (when compared to prior art solutions) the attenuation of EMI noise around the RJ-45 connector.